Help with choosing / using solder paste

[68kbits]

Hi everyone, I have been interested in giving solder paste a shot for a while, but have been able to get by with wire solder, and been put off by the cost and shelf life of the paste.

I bought a hot air station a few months ago for cap removal, and got plenty if good advice from the forum.

I would like to try using paste with the hot air station to assemble a 68060 to 68060 adapter as well as swap a couple chips on an se/30 I'm trying to bring back to life.

Do any of you more experienced guys have some advise to share on which paste to buy, how to store it for max life, and what it is most helpful for?

 

[Elfen]

What do i got? I know I got a syringe of solder paste in the frig. It must be stored cold (not frozen ice cold), and has a 2 year shelf life if stored cold, less than 6 months if stored in room temp. Oh yeah, it's Kester EP256 Solder Paste, date of manufacture: 6/14.

I don't have have a "true" hot air station, but a hot air gun that can melt solder. I also solder with it with a regular iron. It has a higher shelf life if its not opened; there is a seal on on the end of the syringe, that is removed and then the needle tip put in.

It flows smoothly and melts easily. Great stuff. But it takes practice getting it to flow where you want. It has a lot of flux, so when soldering is done, you should wipe the board down with some acetone. And you do not need to use a lot of it, just a dab will do in many cases. If doing an IC's row of pins, just draw a line with it and give it heat. It will pool to the pins and then touch it with a hot solder braid and iron tip if pins are shorted. It just takes practice.

 

[olePigeon]

I have some generic solder paste.  It's been in my garage exposed to the heat and cold for the past five plus years.  It no longer comes out through the metal syringe part, but I squeeze it out like toothpaste, then apply it with a toothpick.  Still works fine, if a bit difficult to use sometimes.  Still easier than normal solder.

 

[bigmessowires]

Good topic. I've never used solder paste either, but I'd like to try it. Is it ok to keep in your regular fridge, with your food? How important is it to use a stencil? I see some people using custom stencils, others like Elfin just squeeze it straight onto a naked board.

 

[olePigeon]

I put it right on the board.  When you melt it with your iron, it pools onto the exposed metal bits.

 

[Elfen]

I think I got mine through Digikey. It went for $14+ S+H for a 2oz syringe. It may not sound like much but its actually a lot since you do not use much of it. I find it an excellent investment. (I've recapped several boards and did a lot of other projects with it.)

I have some generic solder paste.  It's been in my garage exposed to the heat and cold for the past five plus years.  It no longer comes out through the metal syringe part, but I squeeze it out like toothpaste, then apply it with a toothpick.  Still works fine, if a bit difficult to use sometimes.  Still easier than normal solder.

I thought something like that would happen with the paste. Glad it still works for you. No way solder or it's paste would go bad like moldy bread. (LOL!)

 

[68kbits]

Thanks guys. At least it sounds like even when it gets old it's still useful.

I read that the flux separates etc.

Has anyone tried adding more liquid flux and trying to mix it again? Or does the flux in there just turn to a gel like consistency?

 

[Paralel]

No harm in keeping it in the same space with foods as long as its contained.

 

[olePigeon]

I think the moisture just evaporates and it gets thicker, that's about it.  I've never tried mixing in more flux to make it thin again.  As a semi-thick paste, I don't mind it.  Spread it like peanut butter and melt it.